The Valsalva maneuver is known to and used by most pilots and by many knowledgeable air travelers. Its objective is to reduce or to eliminate the pain which is often caused by changes in ambient pressure, usually because of rapid change of altitude.
The problem is grounded in the sluggishness of the sinuses and eustachian tubes for permitting air which is under pressure in the inner ear to leave when ambient pressure is reduced. Air under pressure can readily enter the inner ear, but its exit is slowed by the same passages that permit its more rapid entry. As a consequence, the person can suffer considerable pain as the result of the differential pressure.
These pains can sometimes be relieved by yawning or by stretching the jaws, which favorably affect the sinuses and eustachian tubes to facilitate the exit of air. This is often sufficient for airline and automobile passengers, and for flyers in small aircraft whose rate of change of altitude is relatively small.
However, in the field of high performance aircraft, the rate of climb or descent is often very high, and the amelioration of the problem by means such as yawning is insufficient. For these circumstances, the Valsalva maneuver is a well-known expedient. Of course, it is also useful in less stringent circumstances, and is widely used by pilots and passengers even on low performance craft.
Here it may be observed that this invention is useful in other than vehicular and aircraft environments. In spacecraft and submarine applications, rapid pressure changes are often encountered. This invention is also useful in them.
The purpose of this maneuver is to create a counterbalance pressure to reduce the differential pressure. It is accomplished by pinching the nose closed while keeping the mouth closed, instead of exhaling. However useful, this technique is not available to an airman who is wearing a face mask, and who usually is too busy with his controls to pinch his nose, even if he were not wearing a mask.
At altitudes of most interest to this invention, generally above about 35,000 feet, airmen require assistance in order to breathe. Pressurized breathing systems are known for this purpose. Also, the airman is often provided with pressure suits that keep excessive amounts of blood from going to his feet. As a consequence of these systems, conscious muscular exertion is required for exhalation under many commonly-encountered situations.
In these systems, the airman wears a helmet which carries a face mask. When the mask is in place, it closely fits to his face around his nose and mouth. The volume of the mask is kept small so as to minimize or hopefully eliminate all dead volume. Breathing air is supplied to the mask under pressure through an inhalation valve, and exhaust air is vented from the mask through an exhalation valve. The operation of these valves is entirely in response to the airman's own breathing, which is the reason why conscious exertion is required to exhale against a pressurized system.
Now it will be observed that if the exhalation valve were blocked closed such as by the hand, and the airman consciously tried to exhale, the Valsalva maneuver would be accomplished. One problem is that the exhalation valve is on the mask, at a location not conveniently available to the airman, and which is impeded by other equipment such as the visor and the suspension straps.
It is an object of this invention to make the Valsalva maneuver available to an airman who is wearing a face mask, in a pressurized breathing system by providing a valve which for convenience will be called a "Valsalva valve", and which can be located where it can conveniently be actuated without disturbing other systems such as heads up displays.
It is another object of this invention to provide a control for the Valsalva valve which is conveniently located to the user so he can actuate the valve under physically stringent conditions, such as substantial g loads.